Outdoor Wood Furnace Info
Outdoor Furnaces - Manufacturers with NON EPA-Certified Models Only => Home Made => Topic started by: chaikwa on November 18, 2014, 10:11:57 AM
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There will probably be as many different opinions on my questions as there are snowflakes in a snowstorm, but I gotta start somewhere!
Last year I bought a Hawken OWB as I didn't have enough time to build my firewood processor AND an OWB, and I could afford to buy an OWB but not a processor, so I concentrated on the processor. For those of you interested, the Hawken has performed as they said it would altho it chews thru the wood pretty fast. That's understandable tho, considering it's heating upwards of 10,000 UN-insulated square feet. I went thru about 20 cords last season from the second week of January until the first day of May.
Anyways, I'm going to build the next OWB that I will use to heat my shop, office and a new living area that has yet to be built. My questions are general in scope:
1) How much bigger in diameter should the water jacket be in comparison to the firebox?
A lot of the builds I see, and some of the manufactured units as well, have the water jacket only 6 to 8 inches bigger around than the firebox. I would think the more water, the better, but my thinking may be flawed in this regard.
2) Is it better to pull the heated water off the top of the OWB or the bottom?
Again, I have seen both methods used in both the home made and manufactured OWB's.
3) Should the chimney pipe come out the top of the OWB, (vertically), or out the back, (horizontally to a 'tee', THEN to the vertical position)?
I'm sure the answer to these questions will lead me to MORE questions, but I'll keep it short for now.
I appreciate any of you taking the time to give me your insights!
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Well I will start the
ARGUMENT discussion about pulling heat off top or bottom
Some will argue that the coal bed or reaction chamber (in a gasser) is in the bottom, so that is where you should pull from
ALSO, it is harder to suck air into the pump if it pulls off the bottom of the tank
Other will argue that heat stratification causes the hot water to rise, so you should pull from the top (like you would on a DHW heater)
There will be more room to mount a pump @ OWB (whole other arguement)
I personally like to pull from top, because that is what the manufacturer recommended (Central Boiler) :thumbup: and I have my pumps inside my heated structures, not at OWB (this is personally choice).
I would rather sit in a cramped room and fix a pump, then park by butt in a snowbank. Cause pumps always fail at the smae time; holiday weekend, middle of monster snow storm, middle of the night, while company is over >:( **I also have a few extra pumps (not permanent replacements) laying around for such an occasion, system will not be 100%, but at least the water will keep moving. :thumbup:
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... that heat stratification causes the hot water to rise, so you should pull from the top (like you would on a DHW heater)
That's whaqt makes the most sense to me too, but the one I have now pulls off the bottom because "It makes for a more balanced water jacket". I'd like to hear more discussion about this!
And I agree about the pumps failing at the worst time. I keep forgetting to get a spare for just such an occasion too.
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meh on a spare, my original grundfos is going on fifteen years old, runs just fine. A LOT easier to get air out of the lines when the pump is at the back of the stove.
Depends on the application, hottest part of a gasser is the reaction chamber, cooler water should be returned there and pulled from the top. On a conventional hottest part is usually the top so return cooler water there and pull off the bottom.
Personally I think there is a lot less chance of rain entering the stove if the first part of the exhaust is horizontal.
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I feel like exhaust out the top of the firebox is an easy escape for heat.
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I feel like exhaust out the top of the firebox is an easy escape for heat.
That too, no need to make it any easier to loose BTU's.
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I'm glad this discussions is happening, I converting my OWB to run on WMO and have been burning WMO for a while now so most of the bugs are out.
What I have been wondering is whether I should reduce the burn chamber by installing fire brick all over making it smaller.
The design of the OWB it pulled the water from the bottom and the return was dumped back in 12-14 inches from top, the chimney exits the back wall near where the return water enters the water jacket.
I was wondering also whether I should put the oil gun high up in the chamber or down low, the chamber this OWB design also had a side coal shute ( I never used but it came in about 12 inches from the floor.
Assuming the OWB manufacturer did his engineering they obviously did it for a reason.
It has 4 tubes carrying water thru the top of the fire chamber making me wonder if the gun should be up high licking those pipes.
not sure if any of this helps the thread but//
PS just notice my post has me as a newbie even though I Joined March 2008 Oh well :)
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